The grinding of the tooth flanks of gears and gear-like workpieces with premachined hardened teeth is a machining process which, to achieve a high economic efficiency and adequate grinding quality, must be cooled with a cooling lubricant. In order to attain an optimum cooling/lubrication, a liquid jet of a suitable pressurized cooling lubricant is directed at an optimum angle onto the periphery of the grinding wheel and into the grinding gap between the grinding wheel and workpiece. This is produced by a jet-forming coolant nozzle usually arranged and adjustable on the grinding spindle headstock or work spindle headstock, the position of which said nozzle relative to the grinding wheel or workpiece must be set appropriate to the process by the machine setter prior to beginning the machining process.
A deficient setting of the coolant nozzle results in the process being inadequately cooled and, due e.g. to overheating, the workpiece having an inferior surface quality or other deficiencies, making it unusable. Moreover due to too high temperatures of the contact surface between grinding wheel and workpiece, or to flying sparks, a deflagration of the coolant liquid and air mixture can be triggered in the machine working area, which can set fire to the machine. For this reason the correct setting of the coolant nozzle by the setter or operator on changeover to a new workpiece, for example, or after a grinding wheel change is of great importance.
This situation is taken care of in practice by thorough training of the setting and operating personnel. Another known measure for ensuring a correct setting of the coolant nozzle is the blocking of the process start by the machine control system, which is only released when the setter or operator has confirmed expressly by touch-button that the position of the coolant nozzle relative to the point of grinding is set correctly. The disadvantage of this solution is that the confirmation of the setting of the coolant nozzle offers no sure guarantee that the setting has been undertaken really according to specification, and that the risk of scrap and machine fire is not entirely excluded.
A further known measure by which at least a machine fire can be prevented is the incorporation of a fire extinguishing system in the machine working area, which is activated e.g. by a deflagration. Such a system is expensive, however, and in the event of a deflagration due to an incorrect setting of the coolant nozzle, fails to prevent a long production-impairing interruption of the machining process while the quenching medium is removed from the working area of the machine. Nor does it prevent the production of scrap as long as no deflagration takes place.